1. Field of the Invention
The present invention relates to a plasma tube array-type display sub-module comprising a plasma tube array having a plurality of plasma tubes arranged in parallel, and a display device. More specifically, the present invention relates to a plasma tube array-type display sub-module which can be attached reliably to a sub-module frame without causing any troubles on a plasma tube array even in a case where an address electrode support sheet on the back side of the plasma tube array has irregularities, and a display device.
2. Description of the Related Art
As a technology for realizing a next-generation large-screen display device, a plasma tube array-type display sub-module has been developed with a structure that a plurality of plasma tubes each filled with a discharge gas is arranged in parallel. For example, a large-screen display device having a scale of several meters by several meters in size can be constructed of a plasma tube array-type display system module that a plurality of plasma tube array-type display sub-modules of one square-meter in size is joined to one another. The display device of such a type that the plurality of plasma tube array-type display sub-modules is joined to one another does not need either a large glass substrate to be handled, like an LCD, a PDP and the like, nor a large-scale facility and achieves even image quality at low cost.
Typically, a large-screen plasma tube array-type display device can be constructed as follows. That is, a plasma tube array-type display sub-module is prepared in such a manner that a plasma tube array is integrated with a structural body called a sub-module frame of a certain size. Then, the plurality of plasma tube array-type display sub-modules is joined to one another. Herein, the “plasma tube array-type display sub-module” refers to a display film component as described above which includes a plasma tube, that is, a semi-finished product of a display panel, which dos not have a drive circuit, a power supply circuit and the like incorporated. FIGS. 1A to 1C are perspective views each of which shows a schematic configuration of a plasma tube array of a conventional plasma tube array-type display sub-module. More specifically, FIG. 1A is a perspective view schematically showing the configuration of the plasma tube array of the plasma tube array-type display sub-module. FIG. 1B is a perspective view partly showing the configuration of the plasma tube array of the plasma tube array-type display sub-module. FIG. 1C is a perspective view showing a state that the plasma tube array-type display sub-modules are joined vertically and horizontally to one another.
As shown in FIG. 1A, a conventional plasma tube array-type display sub-module 30 has a rectangular shape as it comprises a part of a rectangular screen and a plurality of plasma tubes 31, 31, . . . each filled with a discharge gas is arranged in parallel. The plasma tube 31 is a discharging thin tube made of glass, which diameter is not particularly limited, but preferably about 0.5 to 5 mm. Herein, for example, the plasma tube array-type display sub-module 30 of one square-meter in size is constructed in such a manner that 1000 pieces of glass thin tubes each having a diameter of 1 mm, a length of 1 m and an oblate ellipsoid section are arranged in parallel by a set of several pieces. The section of the thin tube is not particularly limited in shape, and examples thereof may include a circular section, an oblate ellipsoid section, a square section and the like. Moreover, the plasma tube 31 is filled with a discharge gas such as neon, xenon and the like at a predetermined ratio at a predetermined pressure.
The plurality of plasma tubes 31, 31, . . . arranged in parallel is held between a back-side address electrode support sheet 33, which comprises a plurality of address electrodes 32, 32, . . . formed thereon so as to be in contact with the lower side of the plasma tubes 31, 31, . . . in the longitudinal direction of the plasma tubes 31, 31, . . . , and a front-side display electrode support sheet 35, which comprises a plurality of display electrodes 34, 34, . . . formed thereon so as to cross the upper side of the plasma tubes 31, 31, . . . in the direction orthogonal to the longitudinal direction of the plasma tubes 31, 31, . . . . Herein, the display electrode support sheet 35 is a flexible sheet made of, for example, a polycarbonate film, a PET (polyethylene terephthalate) film or the like.
The plurality of display electrodes 34, 34, . . . is formed in stripes on the inner surface of the display electrode support sheet 35 so as to be contact with the plasma tubes 31, 31, . . . and to cross the upper side of the plasma tubes 31, 31, . . . . The plurality of adjacent display electrodes 34, 34 forming a display electrode pair functions as an X electrode and a Y electrode. Display discharge occurs inside the plasma tubes 31, 31, . . . located between the X electrode and the Y electrode. In addition to the stripe pattern, the pattern of the display electrodes 34, 34, . . . may be a pattern which is publicly known in the relevant technical field, and examples thereof may include a mesh pattern, a ladder pattern, a comb pattern and the like. Moreover, examples of the material for the display electrode 34 may include transparent conductive materials such as ITO (Indium Tin Oxide) and SnO2, and metal conductive materials such as Ag, Au, Al, Cu and Cr and the like.
The display electrode 34 can be formed by various methods which are publicly known in the relevant technical field. For example, the display electrode 34 may be formed by using a thick film technology, such as a printing, or by using a thin film technology such as a physical deposition method or a chemical deposition method. Examples of the thick film technology may include a screen print method and the like. With regard to the thin film technology, examples of the physical deposition method may include an evaporation method, a sputtering method and the like whereas examples of the chemical deposition method may include a thermal CVD method, a photo CVD method, a plasma CVD method and the like.
The plurality of address electrodes 32, 32, . . . is formed on the back side of the plasma tube array-type display sub-module 30 per plasma tube 31 along the longitudinal direction of the plasma tubes 31, 31, . . . , wherein an emit light cell is formed at an intersection of the address electrode 32 and the paired display electrode 34. The address electrode 32 can be formed by various materials and methods which are publicly known in the relevant technical field.
In the configuration described above, as shown in FIG. 1B, the plasma tube array-type display sub-module 30 achieves color display in such a manner that each plasma tube 31 comprises a single-color phosphor layer 36. Examples of the phosphor layers 36, 36, . . . comprise a red (R) phosphor layer 36R, a green (G) phosphor layer 36G and a blue (B) phosphor layer 36B. A set of the plasma tube 31 comprising the red (R) phosphor layer 36R, the plasma tube 31 comprising the green (G) phosphor layer 36G and the plasma tube 31 comprising the blue (B) phosphor layer 36B forms one pixel, so that the plasma tube array-type display sub-module 30 can achieve color display. Herein, the red (R) phosphor layer 36R is made of a phosphor material such as (Y,Gd)BO3:EU3+ in order to emit red light by irradiation with ultraviolet rays. The green (G) phosphor layer 36G is made of a phosphor material such as Zn2SiO4:Mn in order to emit green light by irradiation with ultraviolet rays. The blue (B) phosphor layer 36B is made of a phosphor material such as BaMgAl12O17:Eu2+ in order to emit blue light by irradiation with ultraviolet rays. In order to enhance flexibility of the plasma tube array-type display sub-module 30 and facilitate the assembly thereof, preferably, a plasma tube unit is prepared in such a manner that the plurality of the set of the three plasma tubes for three colors R, G, B is attached to the reed-shaped back-side address electrode support sheet 33 in parallel, and then the plurality of plasma tube units is attached to the front-side display electrode support sheet 35, so that the plasma tube array-type display sub-module 30 for a color display is fabricated.
The perspective view in FIG. 1C schematically shows a plasma tube array-type display system module 45 that the plurality of plasma tube array-type display sub-modules 30, 30, . . . is joined vertically and horizontally to one another. As shown in FIG. 1C, herein, four pieces of plasma tube array-type display sub-modules 30, 30, . . . construct one plasma tube array-type display system module 45 for a large screen. Each plasma tube array-type display sub-module 30 is a semi-finished product which does not have a drive circuit, a power supply circuit and the like incorporated. After construction of the large-screen plasma tube array-type display system module 45, a drive circuit, a power supply circuit and the like are incorporated in the plasma tube array-type display system module 45 defining the whole system module as one display film. Thus, a large-screen display device can be constructed, which has a feature suppressing a variation in quality of images displayed on the respective plasma tube array-type display sub-modules 30, 30, . . . . The plasma tube array-type display sub-modules 30, 30 joined horizontally to each other can be driven simultaneously by connecting the display electrodes 34, 34 in the connection structure according to the present invention. For the plasma tube array-type display sub-modules 30, 30 joined vertically to each other, the respective address electrodes 32, 32 are lead to the upper side and the lower side of the screen so as to be connected to an address drive circuit, whereby the screens of the upper two plasma tube array-type display sub-modules 30, 30 and the screens of the lower two plasma tube array-type display sub-modules 30, 30 can be simultaneously driven by a publicly known method, so-called dual scan technique without connecting the respective address electrodes 32, 32.
As described above, the plasma tube array itself is configured such that the plurality of plasma tubes 31, 31, . . . is held between the address electrode support sheet 33 which is a flexible sheet and the display electrode support sheet 35. Therefore, it is difficult to keep the shape of the plasma tubes 31, 31, . . . , under such a condition. Accordingly, in general, the plasma tube array is attached to the structural body called a sub-module frame to form the plasma tube array-type display sub-module 30, and the plurality of plasma tube array-type display sub-modules 30, 30, . . . is joined to one another to form a display panel for a large-screen display device.
However, the address electrode support sheet 33 on the back side of the plasma tube array might have deformation such as distortion, warpage and the like and the irregularities caused by a projection (burr) on a cutting surface generated upon cutting. Moreover, since a production error is generated on the plasma tube 31 itself, the size such as the diameter is non-constant. Therefore, when the plasma tube array is held between the address electrode support sheet 33 and the display electrode support sheet 35, irregularities might also be generated on the display electrode support sheet 35.
When the plasma tube array is attached to a flat sub-module frame, called a support plate, with such irregularities generated, the back side of the plasma tube array is forced to be flattened on the surface of the sub-module frame, which causes a stress and the like to arise problems of the deformation of the plasma tube array, generation of residual stress, separation of the address electrode support sheet 33 or the display electrode support sheet 35 from the plasma tube array, and the like.
Since the plurality of plasma tubes 31, 31, . . . is arranged in parallel, the shape of each plasma tube 31 slightly varies due to the pressure variation or temperature change inside the plasma tube 31, when a drive voltage is applied thereto. Moreover, the production precision itself varies for each plasma tube 31, wherein the size, i.e., the diameter, of each the plasma tube 31 varies. These factors are correlated with each other, resulting in that, depending upon a drive input pattern, resonance occurs with a vibration mode specific to the plasma tube array, and therefore, an abnormal noise is generated from the surface of the plasma tube array.
In order to avoid the abnormal noise leaking from the front side of the display device, a noise insulation film with a noise insulating effect has to be provided on the front side of the display screen. For example, JP 2003-043937 A discloses a display filter (film) aiming to ease shock of a plasma display. This filter can ease the external shock, but JP 2003-043937 A does not disclose nor suggest the function to avoid the abnormal noise, which is generated from the inside, leaking to the outside.